JP3333960B2 - Method for producing hydrochloride and caustic amino acid using water splitting by electrodialysis - Google Patents

Abstract

The invention uses a stack of three compartment electrodialysis cells in a process for the production amino acid hydrochloride and an alkali. The electrodialysis cell contains bipolar, cation and anion membranes which are arranged to form acid, base and salt compartments. The process begins with supplying a salt solution to the salt compartment, water to the base compartment, and a liquid comprising an amino acid to the acid compartment. Preferably, the feed salt is sodium chloride or potassium chloride or lithium chloride. A direct current driving force is applied across the cell to convert the salt solution to an alkali in the base compartments and an amino acid hydrochloride in the acid compartment. The acid and alkali solutions and a depleted salt solution are withdrawn from their respective compartments. A chelating agent may be added to the salt solution before it is fed into the electrodialysis cell.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for co-producing a hydrochloride salt of an amino acid and caustic soda by utilizing water splitting by electrodialysis, using a salt and an appropriate amino acid as starting materials.

The present invention has been devised based on the following findings (a) to (d). (A) The hydrochloride salt of the amino acid generated in the acid product loop of the electrodialysis cell is stably retained in the loop. By being held in the loop in this way, it becomes possible to produce coexisting caustic with a purity enough to be marketed as a commercial product. Ensuring that amino acid components are retained in the acid loop means that the amino acid feed does not need to be subjected to costly purification, even if impurities such as calcium and magnesium are present in the feed. It means that. (B)
Chlorine passing through the bipolar membrane to generate the hydrochloride salt in situ is substantially reduced, thereby producing caustic of superior quality than that obtained by simply converting the salt to caustic soda and hydrochloric acid. can do.
(C) The method for producing the hydrochloride has high process efficiency and reduces the total production cost. (D) Highly concentrated hydrochloride can be efficiently produced and processed.

The method of the present invention comprises a three compartment electrodialysis (E) having a bipolar membrane, a cation exchange membrane and an anion exchange membrane.
D) Implemented in the cell. A bipolar membrane is a membrane that splits water and does not allow anions or cations to pass. Typically, the salt feed to the cell is almost saturated, and is the dissolution of rock salt (or similar salt source) using fresh water and / or depleted water returning from the cell. . The highly concentrated salt solution is then purified using pH adjustment / filtration and optionally a finishing ion exchange resin. The purified aqueous solution is supplied to the salt loop of the cell.

In the salt loop, ethylenediaminetetraacetic acid (ED
When a small amount of a chelating agent / sequestering agent such as TA) is added, it has a chelating effect on the remaining polyvalent cation impurities (especially calcium), thereby preventing contamination of the cation exchange membrane. Therefore, it is effective in improving the reliability of the process. The high selectivity and efficiency of the production of the hydrochloride salt will keep the salt loop basic (pH> 7), thereby ensuring the stability and solubility of the chelate complex (with polycationic impurities) Is promoted, so that the chelating action becomes even stronger. Thus, the complex will be retained in the salt loop. For this reason, usually
It is not necessary to apply the salt feed to the finishing ion exchange resin.

The process of the present invention can be used for the production of hydrochlorides of various amino acids, as well as for the co-production of high quality caustic. The method is particularly useful for producing the basic amino acids (arginine, lysine, hydroxylysine, histidine) and the hydrochloride salts where there are more than two carbons. The method of the present invention is particularly useful for producing lysine hydrochloride. Type of salt to be treated (NaC
l or KCl or LiCl), the base produced is caustic soda (NaOH) or caustic potash (KO).
H) or lithium hydroxide.

Amino acids are produced on a commercial scale by sugar fermentation or chemical synthesis. Many of these have been isolated or sold in their hydrochloride form. Lysine hydrochloride is one example, and is produced by reacting purified lysine base with concentrated hydrochloric acid. The acids used are often purchased from by-products or chlor-alkali manufacturers. They make concentrated hydrochloric acid by reacting chlorine with hydrogen and dissolving the resulting hydrogen chloride gas in water. The cost of purchasing hydrochloric acid is usually quite high. Also, when dealing with acids, supply, delivery, and safety issues must be addressed.

Another method of producing caustic and hydrochloric acid directly from salt is electrodialysis (E) using a bipolar membrane.
D). Bipolar membranes split water, anions,
Does not pass any of the cations.

FIG. 1 shows a three-compartment cell for carrying out the present invention. The cell contains a bipolar membrane (symbol-+) 4
6. Anion exchange membrane (-) 50, cation exchange membrane (+)
48, which are arranged while repeating this order. The space between the membranes constitutes three compartments of the electrodialysis cell, which are named acid chamber (A), base chamber (B) and salt chamber (S). The membrane and compartment are collectively referred to as a "unit cell" or simply a "cell". Many (possibly 100 to 200
Such a cell consists of a set of electrodes (anode + and cathode-)
And form a compact "electrodialysis stack".

The supply flow of the salt solution enters a salt chamber S sandwiched between the cation exchange membrane and the anion exchange membrane. As shown in FIG. 1, water enters the acid chamber A and the base chamber B on both sides of the bipolar membrane 46. When a direct current is applied to give a propulsive force, H ⁺ and OH ⁻ ions generated at the bipolar film move to the acid chamber A and the base chamber B, respectively. at the same time,
Cl ⁻ and Na ⁺ ions generated by dissociation of the salt (NaCl) pass through the anion exchange membrane 50 and the cation exchange membrane 48, respectively. In the base chamber B, Na ⁺ ions
Combined with H ^- ions to form a base product. Similarly, in the acid chamber A, Cl ⁻ and H ⁺ combine to form an acid product.
Taken together, the salt (NaCl) produces a relatively pure acid (HCl) and base (NaOH) product.

NaCl + H ₂ O = NaOH + HCl

In terms of both equipment and energy costs, ED
The method is less costly than the chlor-alkali method. But E
In method D, only dilute hydrochloric acid (2 to 7% by weight) and dilute caustic soda (5 to 18% by weight) can be produced. Attempts to produce concentrated hydrochloric acid from dilute acids require more costly concentration.

Furthermore, since bipolar membranes do not have complete permselectivity, small amounts of Cl ^- and Na ⁺ ions pass through the bipolar membrane and contaminate the product. That is, a small amount of chloride ion is mixed in the caustic product, and a small amount of sodium ion is mixed in the acid product. The production of dilute acids and bases from salts can lead to 1-4
Mole percent chlorine and acid products have been reported to be contaminated with 2-5.5 mole percent sodium (KN Mani,
"Electrodialysis Water Splitting Technology", J.
Membrane Sci., (1991), vol. 58, 117-138). When such a degree of contamination is present, there arises a problem that the raw material (that is, NaCl) is lost, and the value of the product acid or base is reduced.

One way to improve the caustic and / or acid purity is to use a multi-chamber cell with two or more bipolar membranes, as disclosed in US Pat.
No. 838, No. 5,135,626, No. 5,16
2,076, 5,198,086, 5,20
No. 0,046. However, the cell structures in these patents are more complex and expensive than three-compartment cells.

It should be noted that in the method of producing the hydrochloride of an amino acid by reacting the amino acid with concentrated hydrochloric acid HCl, even if a certain amount of sodium is mixed, it does not cause a serious problem. This is because the hydrochloride product is usually crystallized and removed from solution. However, the inclusion of sodium in the hydrochloride is economically problematic. There is a need for a novel method that can directly produce an amine hydrochloride using salts and amino acids as raw materials. It is also important that the co-produced caustic be of high quality and marketable.

A feature of the present invention is that the method for producing an amino acid hydrochloride and an alkali is carried out by a three-compartment electrodialysis cell comprising a bipolar membrane, a cation exchange membrane, and an anion exchange membrane. is there. With these membranes,
An acid room, a base room, and a salt room are divided.

[0016]

SUMMARY OF THE INVENTION The method begins by supplying a salt solution feed stream to a salt chamber, water to a base chamber, and a liquid containing amino acids to an acid chamber to dissociate the salt. . Preferably, the salt feed stream is sodium chloride or potassium chloride. Then, when a direct current is applied to give a propulsive force, the salt is decomposed and changed into an alkali in the base chamber and a hydrochloride of an amino acid in the acid chamber. The acid product, the alkali product, and the spent salt solution are then drained from each compartment.

[0017] Preferably, the feed stream of the salt solution is purified prior to introduction into the salt chamber to reduce polyvalent contaminants to a preferably low level. It is also possible to add a chelating agent to the salt solution supply stream before supplying it to the electrodialysis cell. The production of the hydrochloride salt of the amino acid in this manner also substantially suppresses the incorporation of chlorine into the co-produced caustic (that is, co-produced with higher purity). The present invention and its embodiments will become apparent from the above specification when read in conjunction with the following drawings.

[0018]

DETAILED DESCRIPTION OF THE INVENTION In an ED process using a bipolar membrane, the amino acid can be directly reacted with the hydrogen chloride formed therein in an acid loop to produce the hydrochloride salt, thereby making concentrated hydrochloric acid available. The present inventor has found that the problems of danger and cost can be avoided. The reaction occurring in the acid loop of the cell is the reaction of the amino acid with the concentrated HCl (30-35% by weight) produced there. The problem of product dilution does not occur as in the prior art. As a result, the hydrochloride salt of the amino acid produced by the method of the present invention has essentially the same quality as that produced by the current process in which the purchased (concentrated) hydrochloric acid is separately reacted. .

The idea of converting immediately into a product on the spot is described in K. N. It is also described in the literature of KN Mani. One example of such a conversion is SO
In the XAL® process, the caustic generated in the bipolar ED cell is neutralized with sodium bisulfite to produce sulfite (US Pat. No. 4,082,83).
No. 5, No. 4,107,015, No. 5,281,3
No. 17).

However, the present invention for producing an amino acid hydrochloride is specific and novel in the following points. The production, handling and transport of hazardous chemicals (ie concentrated HCl) is not required, yet the quality and concentration of the product is not compromised. Surprisingly, the hydrochloride is very effectively retained in the acid loop. As a result, the co-produced caustic soda is “colorless and transparent”, in which the presence of an amino acid (the amino acid mainly used in the experiment is lysine) cannot be detected. Therefore, the caustic quality is high. At the same time, the salt loop is still colorless and transparent, with no detectable amount of lysine. These facts indicate that lysine hydrochloride production test was carried out for a long time (120
(0 hours or more).

Because the hydrochloride salt is so firmly retained, it is considered useful in the production of most amino acids. This result was obtained, in part, because of the large size of the amino acid molecules (ie, there is an excluded volume effect due to the ion exchange membrane). Another reason is that due to the unique properties of amino acids, they are in a favorable ionic form near the boundary membrane of the acid loop. ("Dianion (registered trademark) Manual
of Ion Exchange Resin an
d Synthetic Adsorbent "Vo
lume II, page 118, Mitsub
ishi Kasei Corporation (19
92)). In the form of ions, the amino acids cannot move out of the acid loop, ie, the ions are acidic near the surface of the cationic bipolar membrane and neutral (or rather alkaline) near the surface of the anion exchange membrane. That's why. On the cationic surface of the bipolar membrane

[0022]

(Equation 1)

On the surface of the anion exchange membrane,

[0024]

[Equation 2]

A schematic diagram of this process is shown in FIG.
Here, lysine (expressed as “Ly”) is used as the supplied amino acid. In the acid loop (A), the supplied lysine reacts with protons (H ⁺ ) generated in the bipolar membrane and chloride ions passing through the anion exchange membrane to generate lysine hydrochloride (lysine · HCl). .

Lysine has two amino groups. Therefore, near the bipolar film, there is a possibility that dihydrochloride (lysine. (HCl) ₂ ) may be formed by combining with the second HCl molecule. All of these (lysine HCl
Or lysine · (HCl) ₂₎ is present in the protonated lysine · H ⁺ form (in FIG. 2 ly.H ⁺ display). This positively charged ion is easily moved away from the bipolar membrane due to the electric field. As shown in the above formula (2), near the anion exchange membrane, a neutral salt is formed by the reaction with the chloride ion, and the neutral salt is not brought close to the ion exchange membrane.

In this way, the hydrochloride is transferred to the bipolar membrane 4
6 and the anion exchange membrane 50, the amino acid could not be found at a detectable level in either the base loop or the salt loop, as described above. Considering the effect of diffusion, very small amino acid molecules (for example, glycine) can pass through an ion exchange membrane in small amounts. However, 3 or more (preferably 4 or more)
In the case of a large amino acid containing the following carbon atom, it can be expected that the direct reaction process for producing the hydrochloride proceeds naturally.

The method is particularly suitable for basic amino acids, ie
Applicable to arginine, lysine, hydroxylysine, histidine and the like. These amino acids are large in size (the number of carbon atoms in the molecule is 6) and cannot easily pass through ion exchange membranes. Preferred are molecules having at least 4 carbon atoms per molecule. Since these have a high isoelectric point, they have a large buffering effect with chloride ions. The isoelectric point (PI) is a pH at which the dissociation of amino acids into cations and anions is equal. Basic amino acids have a high PI because amino groups are more numerous than carboxyl groups.

It has been found that when the hydrochloride of the amino acid is produced, the amount of chlorine mixed into the co-produced caustic soda is substantially less than in the case of the production of hydrochloric acid. This surprising result is thought to be the result of the strong bond between the amino acid and HCl in the acid chamber. Because of this strong bond, free chlorine migrating through the bipolar membrane 46 is effectively reduced. For whatever reason, the caustic products according to the invention are of higher commercial value because they are cleaner than those according to the conventional method.

It has been found that the total process current efficiency when implementing the present invention is clearly higher than the current efficiency in the case of hydrochloric acid production. Current efficiency is calculated using the equivalent of caustic / amino acid hydrochloride produced per Faraday (96500 coulombs) of the input current. Since the current efficiency is high as described above, the energy cost (power cost) and the facility cost (film cost) per unit of the product are reduced.

Preferred as supply salts are sodium chloride and potassium chloride. More generally, alkali metal chlorides such as sodium chloride, potassium chloride, lithium chloride can be used. Which of these alkali metal chlorides is used determines which co-produced caustic is sodium hydroxide, potassium hydroxide or lithium hydroxide.

In the process of the present invention, the salt loop is actually basic (pH about 8) because of the high selectivity of the anion exchange membrane.
~ 14). In this case, the salt solution feed stream contains some OH ^- ions, which will also move to the acid loop. This phenomenon, which is process inefficient,
It turned out to be very small. The reaction between the transferred hydroxyl ion and the amino acid in the acid loop is as follows.

[0033]

[Equation 3]

Or

[0035]

(Equation 4)

When the salt loop becomes basic, the anion exchange membrane that repels it is also basic, especially on the membrane surface in contact with the salt loop. It is considered that the presence of this element makes it easier to retain the hydrochloride salt of the amino acid in the acid loop by the reaction of the above formula (3). Chlanda in U.S. Pat. No. 5,049,250.
Explain that on a similar rationale, amino acids can be efficiently separated from entrained salt impurities.

In order to succeed in driving by the method of the present invention, it is necessary to satisfy the following two factors relating to operation from a long-term perspective. (1) The ion exchange membrane must be free from defects (pinholes, cracks, etc.). The membrane must be long-term durable and must not be contaminated with contaminants in the stream, such as polyvalent cations (calcium, magnesium, etc.) and organics (eg, from amino acid feed streams). If necessary, contaminants must be removed by a suitable pretreatment. (2) The components of the ED cell (i.e., gaskets, end plates, etc. for forming various compartments and securing the membrane) must not have internal leaks during long-term operation. Basically, many commercially available cell formats can be used. A particularly suitable format is described in the applicant's co-pending patent application Ser. No. 08 / 784,050, which has also been used in describing the method of the present invention.

The novel method according to the invention will be better understood in the following examples. All experiments were performed using a pilot facility electrodialysis stack of eight cells in a three-compartment system, as shown in FIG.

The stack 149 has electrodes 154 and 156
There are end plates 150 and 152 fitted with
Through this, liquid is supplied to and discharged from the stack. The gasket was 1 mm thick and formed a compartment between the membranes for the solution to enter. All gaskets are 465c in the center
It has an opening of m ² (0.5 ft ² ), through which current flows. In the center opening, a non-woven mesh screen is fitted, which separates the membrane,
I support it. This nonwoven mesh screen also has the effect of making the flow of liquid turbulent. The internal manifold is formed by arranging the holes made in the gasket. A hole (inlet / outlet) connecting the manifold and the central opening portion supplies and discharges the solution to and from each compartment through the hole.

The stack includes nickel anodes 154 and 154.
Electrode rinse chamber ER158, cation exchange membrane 160 (CM
T, SPS or Nafion 324 (registered trademark), and eight consecutive cells are set. The CMT film is manufactured by Asahi Glass (Asahi Glass), and the SPS film is manufactured by Aqualytics Inc.
The Nafion membrane is manufactured by DuPont. Each of the eight sets of cells is, for example, an acid chamber A164, AHA-2 or AAV when viewed from 162 unit cells.
Anion exchange membrane 174 (AHA-2 is manufactured by Tokuyama
manufactured by kuyama Corporation), AAV manufactured by Asahi Glass Co., Ltd.), salt room S172, SPS cation exchange membrane 1
66, a base chamber B168, and an AQ or BP1 bipolar membrane 170. The AQ film is manufactured by Aquaristics, and the BP1 is manufactured by Tokuyama. Stack 1
Of the eight bipolar membranes of 49, following the last membrane 176, the acid chamber A186, AHA-2 or AAV anion exchange membrane 188, the salt chamber S184, the SPS cation exchange membrane 1
90, base chamber B178, another CMT or SPS
There is a cation exchange membrane 180, an electrode rinsing chamber ER'182, and a cathode 156 made of stainless steel at the end.

The stack 149 having the above configuration was incorporated into a system as schematically shown in FIG. 4 for conducting an electrodialysis experiment. Four pumps (P1 to P4)
And circulation tanks 198, 250, 200 and 2
From 02, respectively, acid chamber (204), salt chamber (240),
Into the base chamber (306) and the electrode rinsing chamber (208)
The solution was circulated at a flow rate of 2.5-4 liters per minute. The nominal volume of each circulation tank is 5 liters.
Acid, base and salt loops were pumped in feed and bleed modes.

In operation, a concentrated salt solution filtered or otherwise pretreated to keep polyvalent contaminants to a very low concentration is removed from the salt supply tank 216 (using pump P5). It was added while adjusting with the electric conductivity controller CIC. The supply tank 216 contains one solution of salt for supply.
Can store up to 86 liters. During operation, tank 25
80-85% of the salt fed to 0 was converted to acid and base. The remaining salt solution was removed from the salt tank 250 by overflow and discarded. The dilution (deionized) water is supplied to a base circulation tank 2 using a flow control pump (not shown).
00. The caustic soda of the product was removed by overflow. Similarly, water or a lysine supply liquid (concentration: 100 to 500 g / l) is supplied to a flow control pump (not shown).
Was used to feed the acid tank 198. The product acid was removed by overflow. Electric conductivity indicator CI and pH
The operating status of the acid loop was monitored with a meter (pH).

Using a cartridge filter F210, a flow meter FM212 and a pressure gauge G214, a clean liquid was flowed at a predetermined flow rate and pressure loss in each circulation loop. Wiring from a DC power supply (not shown) was connected to the anode terminal 224 and cathode terminal 226 of the stack.
The regulator required for current input and voltage regulation was located at the power supply.

The pretreated salt solution, deionized water and / or
Alternatively, a sufficient amount of the lysine feed solution was prepared so that it could be supplied as needed, so that the process could be continued day and night without stopping the process. Preferably, a pretreatment is performed to keep polyvalent contaminants in the salt feed at a low level. Approximately 1
0% by weight of sodium hydroxide is charged. All you need to do during operation is to replenish water regularly to make up for losses due to evaporation and the evolution of hydrogen and oxygen, and to make sure (by titration) that you have a sufficient amount of caustic. It is.

The salt solution to be supplied is as described in G.I. S. It is made by dissolving NaCl having a purity of 98% or more in water, supplied from Robins (GS Robins) or purchased from commercial rock salt. Sodium carbonate, sodium hydroxide and optionally phosphate, oxalate and / or granular carbon were added. When sodium hydroxide or sodium carbonate is added, the pH of the salt solution rises to 9 to 10.5,
Promotes precipitation of calcium and magnesium ions. This solution was passed through a cartridge filter (pore size: 5 μm) and then subjected to nanofiltration. For desalting and nanofiltration
A DK-5 element from Desal Osmonics was used, which has a nominal cutoff molecular weight of about 200 daltons. This element is known to be substantially impermeable to multivalent cations. In a real test, the nanofiltration process gives a clean salt solution, which does not detect magnesium,
It contained 0-15 ppm calcium.

In this electrodialysis process, 80-85% of the sodium chloride in the feed was converted to caustic and hydrochloric acid in the base and acid loops, respectively. Some water also migrates to the acid and base loops as water of hydration.

All experiments were performed with a current input of 50 amps (current density 100 A / ft ² = 1075 A / m ² ). The caustic concentration of the product in the base loop is usually 110-1
At 30 g / l, this controlled the addition of deionized water to the loop and kept constant by discharging the product on overflow. Current efficiency (ie, the equivalent of caustic produced per Faraday of current output) depends on emissions and product concentration (H
Titration using Cl standard solution).

The production of amino acid hydrochloride was tested using lysine as a raw material. The lysine feed in free base form had a pH of about 8.5-10. Lysine was metered into the acid loop where it reacted with the hydrochloride formed. The lysine concentration in the feed solution is in the range of 100-500 g / l, calcium of 10-25 ppm and
m of magnesium. Depending on the injection volume and the concentration of the lysine feed, the pH of the product acid varies from 0.5 to 6.5. The lower number is approximately the lysine salt (lysine).
(HCl) ₂ ), and high pH values correspond to the monohydrochloride (l
ysine.HCl). A for the production of hydrochloride
An HA-2 anion exchange membrane was used.

Taking the mass balance around the acid loop, it was found that calcium and magnesium ions were almost retained in the loop. This means
It could be confirmed from the fact that divalent ions in the base loop and the salt loop were not substantially increased. Therefore,
Feeding the acid loop did not require pretreatment of amino acids to remove calcium and magnesium.

Example 1 A long-term test for the production of lysine hydrochloride was performed using a three-compartment ED cell. During the first 313 hours of operation, the salt feed was treated with sodium hydroxide and sodium carbonate, nanofiltered, and fed to the cell's salt loop with controlled electrical conductivity, as described above. . The operating temperature of the cell was 90-95 ° F (32-35 ° C). In the feed solution after nanofiltration, the calcium content is 0-6.
At ppm, no magnesium was detected. The lysine solution was supplied to the acid loop at a controlled flow rate. The hydrochloride solution was removed by overflow. Lysine was held tightly in the acid loop. Taking the material balance between the feed and effluent acid products, it was found that lysine, calcium and magnesium ions remained in the acid loop.

The product sodium hydroxide obtained from the base loop had a concentration of about 117 g / l on average, was colorless and transparent, and the presence of lysine was not observed. The product caustic contained 100 to 500 ppm of chlorine. The current efficiency for caustic production averaged about 90%.
The total cell voltage was stable at 25-28V. Assuming that the voltage in the electrode rinsing chamber is about 5 V, since there are eight cell units, the voltage per cell set is 2.5 to 2.9 V.
It turns out that.

In the salt loop, the concentration and concentration of the salt feed decreased due to the movement and conversion of the salt ions. The feed contains about 60 g / l of sodium, but the liquid discharged by overflow contains only 12-35 g / l of sodium. The salt overflow is alkaline, 2-10 g / l Na
It contained OH. From this, the anion exchange membrane is
It can be seen that the ability to retain the acid ions generated in the cell is high. The overflow of the salt was also colorless and transparent, and lysine could not be detected by analyzing it.

Example 2 Subsequently, in the next 688 hours, the second experiment was performed. In this experiment, a small amount of chelating agent (EDTA in the form of potassium salt) was added to the salt feed before or after nanofiltration so that the salt feed to the cell contained some amount of EDTA. did. When the salt solution is made from rock salt, activated carbon (80 pounds (3
40 g of activated carbon per 6.3 kg) were also added. The salt solution was subjected to nanofiltration in the same manner as in Example 1, and supplied to the cell while adjusting the electric conductivity. The acid loop and the base loop are under the same operating conditions as in Example 1. Cell operating temperatures were typically in the range of 40-43 ° C (100-115 ° F). At 688 hours of operation, the overflow of sodium hydroxide and salt of the product was colorless and transparent throughout, and no detectable amount of lysine was observed. The caustic concentration and chlorine content were the same as in Example 1.

The salt feed solution contained 2 to 22 ppm of calcium, but no magnesium was detected.
Calcium numbers are higher when EDTA was added to the feed prior to nanofiltration. This addition reduced the selectivity of the nanofilter for retaining calcium. Nevertheless, the mass balance for the salt loop showed that calcium was effectively retained in the salt loop. (No. 09 / 193,626, co-pending by the present inventors (November 1998
Application dated March 11). It was found that the cation and anion exchange membranes surrounding the salt loop had an excellent retention effect on the complex of EDTA and calcium. Thus, contamination, if any, of the cation exchange membrane is very low, as confirmed by the relatively stable cell voltage maintained at about 25-28V. The stable current efficiency of the cell in caustic production of approximately 90% also demonstrates that the cation exchange membrane was stable.

At the end of the test, the cell was disassembled and the inside was inspected. There were no abnormalities in either the gasket or the membrane. This proved that the production process of the hydrochloride of the amino acid can be operated for a long time.

Example 3 An ED cell was reassembled using the bipolar membrane and the anion exchange membrane used in the above test again. A complete set of SPS membranes was used as the cation exchange membrane. A new test with this combination lasted 311 hours. The feed salt solution was prepared as before, but without the addition of a chelating agent and passed through a cartridge filter. The solution was then nanofiltered and further heated to about 70 ° C. before being applied to C-4 from Rohm and Haas.
Pretreatment was performed through an ion exchange column filled with 67 chelate resin. Resin treatment reduced the calcium content in the feed stream to about 0.05 ppm.
The acid, base and salt loops were operated under the same operating conditions as in Examples 1 and 2. Test results, including caustic quality of the product, retention of lysine in the acid loop, current efficiency in caustic production, cell voltage, etc., were similar to those obtained in Examples 1 and 2.

The test results of Examples 1 to 3 are summarized in the graph of FIG. The operation time on the horizontal axis indicates three experiments in succession. That is, the first 313 hours are Example 1, the next 688 hours are Example 2, and the last 311
The time is the data of the third embodiment. Cell voltage and current efficiency are stable, and pretreatment with chelating resin (Example 3)
And the addition of a chelating agent (Example 2) shows that they are substantially as effective in preventing contamination of the cation exchange membrane by calcium.

Example 4 After conclusion of the test described in Example 2, the AAV anion exchange membrane was used instead of the AHA-2 anion exchange membrane,
In the cell of the pilot facility, NaCl was converted to NaOH and HCl.
The test was conducted for 87 hours. The AAV anion exchange membrane is a membrane having a weak basicity, and has high HCl generation efficiency. The test was performed in the same manner as in Example 2, except that deionized water was added to the acid loop, and 5.5 to 6 wt%
In that hydrochloric acid was generated. The product had a caustic soda concentration of about 115 g / l. The salt feed solution was used in Example 1.
And treated for nanofiltration. Chelating agent E
DTA was added to the salt feed solution after nanofiltration. As with Example 2, the material balance showed that calcium was well retained in the salt loop. However, this process resulted in low current efficiency of about 80%.
The salt loop was acidic due to the lower selectivity of the anion exchange membrane compared to the cation exchange membrane. The caustic soda of the product contained 1800 to 2800 ppm of chlorine.

FIG. 6 shows the amount of chlorine mixed in the caustic of the product in Examples 1 to 4 described above. The upper straight line is H
This is the result in the case of Cl production (Example 4), and the molar mixing ratio described in the literature falls within the range of 1 to 4%. The lower straight line is the result for the hydrochloride production (Examples 1-3). The quality of the caustic soda produced by the process of the present invention is quite good and the chlorine contained is HCl
It is 1/10 or less of caustic soda at the time of combined production.

Example 5 The AHA-2 anion exchange membrane used in Examples 1 to 3 was replaced with B
The P1 bipolar membrane and the SPS cation exchange membrane were used in the eight cell units shown in FIG. 3 in combination. The test was performed for 150 hours according to the same procedure as described in Example 3. In this case, the total cell voltage was 25-28V, as in most tests. The current efficiency is a little low,
About 80-84%, probably due to Example 1
This is probably because the selectivity of the SPS cation exchange membrane was different from those used in Nos. 1 to 3. Table I shows the results of a detailed analysis of a set of salt overflow, product caustic, lysine feed, and product lysine hydrochloride stream. As can be seen, lysine is the major component in the feed solution for the acid loop, but there are also some other amino acids. Importantly, all amino acids, even glycine having 2 carbon atoms, are effectively retained in the acid loop and cannot be detected in the salt or base loops.

[0061]

[Table 1]

Table I also shows that AQ and BP were added to the bipolar membrane.
A comparison of the caustic as well as the quality of the acid product when using No. 1 is also shown. Compared with the AQ bipolar membrane, the BP1 bipolar membrane showed a result that sodium movement to the acid loop was slightly less and chlorine movement to the base loop was slightly more. Generally speaking, both membranes produce high quality caustic products. The hydrochloride of an amino acid can also be produced by using potassium chloride as a raw material salt. In that case, what is obtained as a co-product is potassium hydroxide, that is, KOH
It is.

FIG. 7 is a block diagram for understanding the flow of the process. It also describes the utilities used in the present invention for producing lysine.HCl. Lysine, which feeds the acid loop of the electrodialysis (ED) cell, is obtained by fermentation of dextrose (shown at 300 in the upper left of FIG. 7). At the outlet of the fermenter, sulfated impurities (l
_{ys · H 2 SO 4, pH} 2~4) obtained as (or chloride). The solution is purified through an ion exchange column 302, first lysine is eluted with ammonia / ammonium hydroxide. (Lysine is selectively adsorbed to the ion exchange resin, and sulfate ions are converted to ammonium sulfate and discharged from 304. The adsorbed lysine is desorbed using an ammonia solution.) The lysine is placed in the ammonia removal column 306. PH 8-10 obtained with ammonia removal column
A part of the lysine solution is supplied to the acid loop of the ED cell through a pipe 308, and the remaining lysine solution is supplied to the multiple effect can 31.
Send to 0.

The lysine supplied into the acid loop in the ED cell reacts with HCl generated there to form a hydrochloride. Products obtained with acid loops are typically lysin
e · (HCl) x, where x is about 1.5 to 2. Its pH value is between 0 and 2. This is 31
Send to 2 for pH adjustment. Here, for products with low pH,
The lysine concentrated in the multi-effect can 310 is mixed with lysine HCl having a composition of 1 to 1 and a pH of about 5.5.
Get the salt. The hydrochloride then crystallizes at 314 and most of the mother liquor and wash water are passed through 316 tubing to the multiple effect can 31.
Send to 0 and evaporate the water. Lysin as required
Before the e.HCl salt is put into the crystallization step, cations such as Na and K may be removed and purified through a cation exchange column (not shown).

The raw material to be supplied to the ED cell is obtained by adding additional water to the salt solution returned by circulation, dissolving the purchased salt, and making the salt solution almost saturated. Since the spent salt solution returning from the recycle line is usually alkaline, no additional caustic is needed to raise the pH to the range of 9 to 10.5.

To promote precipitation of compounds such as calcium, magnesium and iron, sodium carbonate and / or sodium phosphate are added. The solution thus obtained is filtered at 320 to remove most of the insoluble material and then treated with a 322 nanofilter. The nanofiltrated feed solution is passed through an ion exchange column 324 filled with a cation exchange resin for chelation to further reduce the content of dissolved calcium remaining. In some cases, a chelating agent such as EDTA may be added to the nanofiltered salt feed. The pretreated salt supply liquid is supplied to the salt loop of the ED cell.

In the ED cell, some of the salts are converted to caustic and hydrochloric acid. The spent salt solution overflows at 326 and is withdrawn from the salt loop and returned to the salt dissolution step. Hydrochloric acid generated in the acid loop reacts with the lysine feed to form the hydrochloride salt. According to 328, deionized water is introduced into the base loop to remove the caustic that forms. Concentration 100-20
0 g / l of dilute caustic is discharged from the base loop by overflow and, if necessary, from 45 to 50 in evaporator 330.
Concentrated to weight%. The resulting solution is discharged at 332 to become a product.

Those skilled in the art will readily be able to modify the method of the present invention. Therefore, the appended claims should be considered to cover all equivalent structures and methods without departing from the spirit and scope of the invention.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a three-compartment cell used in the method of the present invention.

2 is a schematic diagram of how the method of the present invention proceeds in the cell of FIG.

FIG. 3 is a schematic diagram of an eight cell electrodialysis stack pilot facility used in the experiments herein;
This stack combines the three-compartment cell configuration of FIGS.

FIG. 4 is a block diagram of a system for implementing the method of the present invention.

FIG. 5 is a graph summarizing the test results described in the examples.

FIG. 6 is a graph showing chloride contamination in the produced caustic at the time of the test.

FIG. 7 is a block diagram of a system used in the present invention to produce lysine HCl.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ identification code FI C07B 61/00 C07C 229/26 C07C 229/26 C02F 1/46 103 (58) Fields surveyed (Int. Cl. ⁷ , DB name ) C02F 1/469 B01D 61/44 B01D 61/46 C01D 1/04 C07B 61/00 C07C 229/26

Claims (15)

(57) [Claims] 1. A method for producing an amino acid hydrochloride and an alkali using a three-compartment electrodialysis cell including a bipolar membrane, a cation exchange membrane and an anion exchange membrane, wherein the membrane is arranged to form an acid. Room, base room, salt room, and the method is
(A) supplying a flow of a salt solution to a salt chamber of an electrodialysis cell, supplying a flow of water to a base chamber of the cell, and supplying a liquid containing an amino acid to an acid chamber of the cell; (b) direct current driving Applying a force to the cell to convert the salt to form an alkaline solution in the base chamber and convert the amino acid to form a hydrochloride in the acid chamber; (c) combining the acid solution and the alkali solution obtained in step (b). And extracting from the respective compartments together with the spent salt solution. 2. The process according to claim 1, wherein the salt stream of step (a) is selected from the group consisting of sodium chloride, potassium chloride or lithium chloride, and the corresponding alkali product is sodium hydroxide, potassium hydroxide or lithium hydroxide.
the method of. 3. Purifying the salt stream prior to step (a) to reduce polyvalent contaminants to a low level prior to introducing the salt stream into the salt compartment in step (a). 2. The method of claim 1, further comprising the step of: 4. The method of claim 1 further comprising the step of adding a chelating agent to the salt stream of step (a) prior to providing the salt stream to the salt chamber. 5. The method according to claim 1, further comprising the further step of converting and concentrating the concentration of the alkaline solution to between 50 and 200 g / l during step (b). 6. The method of claim 5, further comprising evaporating the alkaline solution after step (c) to further increase the concentration. 7. The method of claim 1, wherein the amino acid of step (a) is a molecule containing at least three carbon atoms. 8. The method of claim 1, wherein the amino acid in step (a) is arginine,
The method of claim 1, wherein the method is selected from the group consisting of lysine, hydroxylysine, histidine, and mixtures thereof. 9. The amino acid of step (a) is lysine,
2. The method of claim 1 wherein the acid obtained in step (c) is lysine hydrochloride and contains 1 to 2 equivalents of hydrochloric acid per mole of lysine. 10. The lysine in the step (a) is 100 to 500.
2. The method of claim 1 further comprising the step of concentrating to a concentration of g / l.
The described method. 11. The method of claim 9, wherein lysine is produced by fermentation and then introduced into the electrodialysis cell of step (a). 12. The spent salt solution obtained in step (c) is strengthened and purified by adding a new salt, and the strengthened and purified salt solution is added to the salt chamber of the electrodialysis cell. 2. A further step of recirculating to
The described method. 13. A method for producing lysine hydrochloride, comprising: (a) a step of producing a lysine salt solution by fermentation of an organic substrate; and (b) filtering the solution of step (a), followed by filtration. A step of obtaining a purified lysine solution by desorbing the captured lysine with an ammoniacal base solution through an ion exchange column, (c) dividing the purified solution of step (b) into two, Converting the hydrochloride salt by acidification in a three-compartment electrodialysis cell using a motive force of a direct current supplied with an alkali chloride salt and concentrating the remainder in an evaporator; (d) lysine Combining the two parts of step (c) with pH adjustment in order to obtain a lysine hydrochloride solution in a ratio of about 1: 1 with hydrochloric acid, and (e) the solution obtained in step (d) To precipitate the hydrochloride A method comprising the steps of: 14. Prior to the crystallization of step (e), pass the lysine hydrochloride from step (d) through a cation exchange column to remove contaminating sodium, potassium, calcium,
14. The method of claim 13, including the step of removing at least one cation of magnesium. 15. The method of claim 13, wherein the salt used to provide the hydrochloric acid component is selected from the group consisting of sodium chloride, potassium chloride, or lithium chloride.